Many icosahedral and helical plant viruses produce at high levels in susceptible hosts, with yields in excess of 1 gram/Kg of leaves being common. They have been the subject of assembly studies for decades and have more recently been manipulated genetically through the use of infectious clones. High levels of heterologus expression in E. coli and yeast have also been achieved. Many are well characterized structurally with atomic coordinates available for the capsid protein subunits. These developments for cowpea mosaic virus made it a therapeutic agent for the development of inexpensive vaccines. Likewise, cowpea chlorotic mottle virus has been exploited as a molecular container with the internal properties modified by genetic alteration of the capsid protein. These qualities suggest that plant viruses can serve as a novel biomaterial. The goal of the proposed work is to now use these attributes of plant viruses and to exploit the particles as nanoblocks" and nano containers and to understand the principles of these alterations on their function. We will use plant virus particles as "symmetric dendrimers? that can be chemically modified for developing a variety of targeted bio sensors, centers of catalysis, delivery systems, and imaging agents. We will generate tailored 2 and 3 dimensional arrays of these particles and these will serve as templates for a variety of nano materials. All of the basic technology of virus genetic modification is fully developed for the systems employed, as is the linkage chemistry for generating specific constellations of covalently attached functional groups. Six research groups will collaborate to create a wide range of modified plant virus particles and to explore their properties in vitro and in vivo. The expertise of these groups include synthetic and catalytic chemistry, materials science, the biochemistry and biophysics of nucleoprotein assembly, molecular virology, crystallography, electron cryo microscopy, image reconstruction and solution scattering methods.